find more symbols graffitied on a wall and struggle to decode the message. Back at the museum, Holmes surprises Soo Lin in hiding, who explains the code is linked to the criminal ring "Black Lotus Tong", of which she was once a member. Unfortunately, before she can fully decode the message, she is killed by her brother, another criminal gang member. Sherlock realises Van Coon and Lukis were members of the Tong, involved in smuggling valuable antiquities to sell in London. They were killed because one of them stole something. Sherlock knows the message is in the form of a book cipher, and he and John spend the night going through the first two victims' books, trying to find the solution. John's first day at work does not go well, but Sarah covers for him, and they organise to go out on a date. Sherlock arranges tickets to a travelling Chinese circus. While John and Sarah enjoy the classic escapology and acrobatics acts, Sherlock snoops around backstage and is attacked, but with Sarah and John's help, the three escape. While Sherlock continues to search for the solution to the book cipher, John and Sarah are kidnapped; John is mistaken for Sherlock by the villains, who want him to reveal the location of the missing "treasure" in return for Sarah's life. Fortunately, Sherlock cracks the code using an A-Z London Street Atlas guide, and rescues John and Sarah. He also realises the elusive "treasure" has been in plain sight all the time: A jade hairpin belonging to the Chinese royal family, worn by van Coon's secretary/mistress Amanda (Olivia Poulet), who had received it as a gift from van Coon. However, Shan, the Black Lotus Tong's leader, escapes and contacts a person via online "chat" identified only by the initial "M" who had helped the gang to get a foothold in London. The episode ends a moment before a sniper shoots Shan after "M" types that Shan will not fail again. Allusions According to Moffat, the episode takes the concept of coded messages from "The Adventure of the Dancing Men" (using pictorial messages), a story feature directly referenced later, in the series 4 episode The Final Problem. Alan Kistler of Newsarama has pointed out other potential inspirations such as the use in The Valley of Fear of a code "based on a book that many people would own." A murder victim found